1. Field of the Invention
The present invention relates to a method for bonding of stitched carpets.
2. Description of the Prior Art
Published application WO 00/52246, the PCT counterpart of co-pending application U.S. application Ser. No. 09/260,749, filed Mar. 2, 1999 and assigned to the assignee of the present invention, discloses a stitched pile surface structure having a thermoplastic binder disposed in the vicinity of the roots of the pile elements. To be most effective the binder material should penetrate into the roots of the pile elements and into the interstices between the filaments forming the same.
Disposing the binder material in these locations requires some care, as the operating temperature window for binder processing is, in most cases, relatively narrow. On one hand the binder must have a melting temperature that is sufficiently high so that the binder remains set when exposed to the expected maximum end-use temperatures for a pile surface structure, typically in the vicinity of eighty degrees Centigrade (80° C.). On the other hand, processing the binder at too high a temperature may negatively affect the material from which the pile elements are made. For example, in the case of nylon pile elements, temperatures in excess of approximately one hundred twenty degrees Centigrade (120° C.) may adversely affect certain properties of the nylon material forming the pile elements.
Accordingly, it is not simply a matter of raising the temperature of the binder to an extent that the binder freely flows into the desired locations in the pile surface structure.
In view of the narrow temperature operating window it is imperative that physical pressure be exerted while the thermoplastic binder is molten but not freely flowing, to help the binder propagate into the desired bond areas.
It should be noted that care must also be exercised when applying pressure to the pile surface structure.
Applying nip pressure, by pressing from above and below with pressure rolls, is a mechanical expedient occasionally used in the industry to apply pressure to a pile structure. However, nip pressure may have the undesirable side effect of “matting”, or “crushing”, the pile.
Accordingly, in view of the foregoing it is believed desirable to provide a process, which utilizes a binder material with a relatively low melting point so that the binder can be processed at a temperatures under the critical temperatures that adversely affect the pile material. The process should, at the same time, be practiced in a physical environment in which pressure may be brought to bear on the pile to cause the thermoplastic binder to propagate without crushing of the pile. It is believed to be of further advantage to achieve this result while the pile surface structure is subjected to usual industry finishing processes, such as scouring, dyeing and drying.
In accordance with the present invention a thermoplastic binder is applied in the vicinity of the roots of a pile surface structure, typically before stitching. The binder material is raised above its melting point but below the critical exposure temperature that can adversely affect the properties of the material forming the pile elements. While at this elevated temperature the pile surface structure is mechanically flexed, as by repeatedly bending the backing with the pile loops thereon into and out of its plane. This flexing action assists the molten (but not freely flowing) binder to propagate into the roots of the pile elements and into the interstices between the fibers forming the same. In the preferred implementation the process is practiced using conventional dyeing systems wherein the temperature is customarily raised and flexing customarily employed to promote dye propagation and dye setting. The process may also be practiced in equipment, which flexes the heated pile structure over small-diameter rolls or bars.
Optionally, the pile structure may be scoured before the flexing step, and/or, subjected to a final heating step without flexing.
The invention will be more fully understood from the following detailed description, taken in connection with the accompanying drawings which form a part of this application, and in which:
Throughout the following detailed description similar reference numerals refer to similar elements in all figures of the drawings.
With reference to
The pile surface structure 10 includes a backing 14 having an upper surface 14S and a lower surface 14L thereon. An array of pile yarn elements 16 is stitched to the upper surface 14S of the backing 14.
The pile yarn elements 16 are formed using a stitching apparatus of the type having a sinker bar carrying an array of sinker fingers. Details of a suitable stitching apparatus are set forth in published application WO 00/52246, the PCT counterpart of co-pending application U.S. application Ser. No. 09/260,749, filed Mar. 2, 1999 and assigned to the assignee of the present invention.
Briefly summarized, the stitching apparatus used to form the pile surface structure includes a transversely extending sinker bar from which extends a plurality of sinker fingers. The sinker fingers project forwardly past a needle plane defined by the reciprocating operation of an array of stitching needles. The backing 14 is conveyed through the stitching apparatus so that successive transversely extending regions of the backing 14 are advanced into the needle plane. Stitching threads from adjacent thread-carrying guide bars are successively looped around respective spaced locations on a length of yarn dispensed from a yarn guide bar.
As successive transverse regions of the backing 14 move into the needle plane pairs of adjacent first and second needles are actuated and raised through the backing to positions above the sinker fingers. In the raised positions the adjacent needles respectively successively engage the looped stitching threads and draw these stitching threads toward the backing 14. These actions draw the length of dispensed yarn to the surface 14S of the backing 14.
As the adjacent needles draw the threads downwardly toward the backing 14 the dispensed length of yarn becomes trained over the surface of the sinker finger, thereby forming a laid-in pile yarn element 16 overlying above the first surface 14S of the backing 14. Continued downward movement of each needle through the backing 14 forms an underlap portion 20U of a chain stitch 20. The underlap 20U of the stitch 20 secures the pile yarn element 16 against the first surface 14S. Each stitch 20 also includes an interlockable looped overlap portion 20L that lies against the bottom surface 14B of the backing 14. Sequential overlap portions 20L typically interlock with each other, chain-fashion, longitudinally along the bottom surface 14B of the pile surface structure 10.
In a loop pile embodiment illustrated in
As is illustrated by the dot-dash lines in
A binder material assists in securing the pile element 16 to the upper surface 14S of the backing 14. In
More particularly, the final solidified binder material 24S is concentrated:
Substantially all of the filaments of the pile yarn and the interstices therebetween in the distended regions 16D of the root portions of substantially all of the pile elements 16 have set binder material 24S present thereon. At least the upper two-thirds of each pile yarn element 16 remains substantially free of binder material.
The initial step in accordance with the present invention is the application of a thermoplastic binder material having a predetermined melting point in the vicinity of the root portion of the loops. This binder application is generally indicated throughout these
Whatever its physical form, in the preferred instance the binder material is an amorphous binder. Typically, the melting point of the amorphous thermoplastic binder lies in the range from about eighty-five to about one hundred degrees Centigrade (85-100° C.). An amorphous thermoplastic binder tends to flow more readily than a thermoplastic binder in the form of film or strands.
As will be developed the amorphous thermoplastic binder is most preferably in the physical form of a powder having particles with sizes in the range from about one (1) to about five hundred (500) microns. A suitable amorphous thermoplastic binder material useful for the purpose here described is that available from EMS Corporation, Ems Switzerland, as Griltex 1500A P-1 powder.
The most preferred technique of binder application is to apply an amorphous binder material to the surface 14S of the backing 14 in the form of a dry powder. The binder powder is scattered from a dispenser 28 onto the upper surface 14S of the advancing backing 14. Suitable for use as the dispenser is a scattering device manufactured and sold by the Herbert Meyer Company, Roetz, Germany.
It lies within the contemplation of the present invention to mix with the binder powder a small percentage of a secondary thermoplastic adhesive powder. Preferably the secondary thermoplastic adhesive powder also has particle sizes in the range from about one (1) to about five hundred (500) microns and a melting point in the range from about five (5) to about twenty (20) degrees Centigrade ° C. below the melting point of the primary binder powder. The secondary thermoplastic adhesive powder is on the order from about five percent (5%) to about twenty percent (20%) of the weight of the primary binder. A suitable thermoplastic material useful for the secondary thermoplastic adhesive powder is that available from EMS Corporation, Ems Switzerland, as Griltex 1531A.
After the primary binder powder (or the mixture of the primary binder powder and the secondary thermoplastic adhesive powder) is applied the backing is heated to a predetermined temperature. This heating step is generally indicated by the reference character 30. Any suitable heating device may be used to implement the heating step, such as an oven, a radiant heater or a hot gas heater. The predetermined temperature to which the backing 14 is heated is dependent upon whether the binder powder alone or the powder mixture is applied to the surface 14S. If only a primary binder powder is applied to the surface 14S, the backing 14 is heated to a temperature slightly (on the order if a few degrees) greater than the melting point of the primary binder powder, thus melting the primary powder binder and attaching the same to the backing 14. After solidifying downstream of the heating device a layer of the primary powder binder (indicated by the reference character 24L in
If a mixture of a primary binder powder and a secondary thermoplastic adhesive powder is applied to the surface 14S, the backing 14 is heated to a temperature slightly greater than the melting point of the secondary thermoplastic adhesive powder but less than the melting point of the primary binder. Heating to this temperature melts the secondary thermoplastic adhesive powder. When solidified after leaving the heating device a layer of the primary powder binder supported in an adhesive matrix (indicated by the reference character 24L′ in
The backing 14 with the binder material 24L, 24L′ applied to the surface 14S thereof is next stitched, as indicated by the reference character 32, using a stitching apparatus such as the one described above. In the stitching apparatus the pile elements 16 are formed on the backing 14 in the manner above discussed. Accordingly, as illustrated in
In accordance with the present invention, after formation, the pile surface structure 10 is mechanically flexed into and out of the plane of its backing 14 at a temperature greater than the melting point of the binder. This mechanical flexing at the elevated temperature is indicated by the reference character 34. The term “mechanically flexing” (or a similar term) of the pile surface structure 10 into and out of the plane of its backing 14 is meant to denote repeatedly folding and counter-folding the backing in such a way that portions of the pile surface and portions of the backing are alternatively brought toward and away from each other.
The elevated temperature causes the binder material to melt. The flexing action imposes mechanical forces on the then-molten binder causing it to flow and to penetrate into the root portions of the pile loops in the vicinity of the stitching thread underlaps holding the same to the backing and into the interstices between the filaments forming the pile loops.
In one embodiment of the invention the temperature at which the flexing occurs is maintained by immersing the pile surface structure 10 in a liquid having a temperature greater than the melting point of the binder. An example of a suitable apparatus 40 in which the immersion and flexing occurs is illustrated in diagrammatic form in
In operation, a length of pile surface structure 10 is formed into an endless loop that is trained over the rotors 44. Preferably, the lower surface 14L of the backing 14 engages against the rotors 44 to avoid crushing of the pile elements 16 on the upper surface 14S of the backing. Portions of the pile surface structure 10 are folded and counter-folded upon themselves both upstream and downstream of each rotor. Some folding of the pile surface structure, such as that indicated by the reference character 46F, causes the pile elements on portions of the pile surface structure 10 to be brought toward each other while portions of the backing are simultaneously brought away from each other. Alternatively, counter-folding, such as that indicated by the reference character 46C, brings portions of the backing toward each other while pile elements on the opposite surface of the backing are brought away from each other.
The folded and counter-folded portions of the pile structure are submerged in the liquid 48 disposed in the lower portion of the enclosure 42. The liquid 48 is maintained at the desired temperature sufficient to melt the binder material. As the rotors 44 rotate in the directions indicated by the reference arrows 50, the pile surface structure 10 is drawn from the liquid bath 48 and is continuously flexed as the backing 14 of the pile structure 10 folds and unfolds into and out of the liquid bath 48. Each progressive reversal of direction in the backing 14, both within the bath 48 as well as over the rotors 44, flexes the backing 14 into and out of its plane. This mechanical flexing action creates pressure in the pile elements 16 and causes the then-molten binder to flow into the root portion of the pile loops and into the interstices of filaments forming the pile elements. The pile surface structure 10 is subjected to the treatment described for a suitable period of time, e.g., in the range from about several minutes to several hours.
As may be appreciated, a standard Beck dye chamber may be used to effect suitable mechanical flexing action in the elevated temperature liquid.
In another embodiment of the invention the temperature at which the flexing occurs is maintained by passing steam or a heated gas having a temperature greater than the melting point of the binder over the pile surface structure 10. An example of a suitable apparatus 54 for this purpose is illustrated in stylized diagrammatic form in
In operation, a length of pile surface structure 10 is threaded over the rollers 58 and the abutments 60. The pile surface structure 10 is drawn through the enclosure 56 by the action of a pair of nip rolls 62 disposed in a convenient location, such as adjacent to the exit port 56P′. Preferably, those rollers 58 which interface against the pile elements 16 (i.e., the lower rollers 58 in
The pile surface structure 10 is drawn into and through the enclosure 56 by the action of the nip rolls 62, as indicated by the reference arrows 64. The pile surface structure 10 is thus conveyed, in serpentine fashion, over and under the rollers 58 and/or the abutments 60 mounted within the enclosure 56. At the same time the pile surface structure 10 within the enclosure 56 is subjected to a flow of steam or hot gas (such as hot air) introduced into the enclosure, as from suitable jets 66 provided for that purpose. The temperature of the steam or hot gas is sufficient to melt the binder material on the pile surface structure 10.
Each reversal of direction of the pile surface structure over or under the rollers 58 and/or the abutments 60 folds and counterfolds the backing 14 of the pile surface structure into and out of its plane (as again indicated by the reference characters 46F, 46C), similar to the mechanical flexing action discussed in connection with
Yet further, a second pairs of nip rolls 68 (with pins 68P) may be mounted within the enclosure 56. These nip rolls 68 serve to force a length of the pile surface structure 10 into a U-shaped region defined between plates 70 and thus, further flexing the pile structure 10.
Prior to mechanically flexing the pile surface structure 10 may be scoured in a vat of heated liquid to remove substantially all oil and finish from the pile loops. This action is indicated diagrammatically in
After the flexing action is completed, especially if the flexing is carried in the presence of the heated liquid or steam, the pile surface structure is dried, as indicated by step 38. Any suitable dryer apparatus may be used. A suitable time-temperature profile would dry the pile surface structure at a temperature of at least one hundred ten degrees Centigrade (110° C.) for at least two (2) minutes, to improve plastic flow and adhesion during drying.
The finished pile surface structure (
In another alternative embodiment, as diagrammatically illustrated in
After application of the binder the backing 14 is conveyed directly (i.e., without heating) to be stitched, where the pile surface structure 10 is formed in the manner described. The remaining steps of the method may be implemented as described in connection with
The slurry may alternatively be applied by padding onto the surface 14S of the backing 14.
After application of the slurry the backing 14 is again heated, as indicated by block 30. In the heating device the surface of the backing 14 is heated to a temperature that is above the evaporation temperature of the vehicle, above the setting temperature of the soluble adhesive, and below the melting temperature of the powder binder. As a result a layer of binder supported in a matrix of adhesive is disposed over the surface of the backing. The layer is similar to the layer 24L′ shown in the diagrammatic view of
In accordance with this embodiment of the invention, after stitching the pile surface structure 10 is soaked, as indicated at reference character 39, to dissolve and remove the adhesive matrix. Scouring may also be performed with the soaking, if desired.
After soaking the pile surface structure 10 is flexed into and out of the plane of the backing, as discussed in connection with block 32 in
As illustrated in
The binder material may alternatively or additionally be introduced into the pile surface structure as part of a composite stitching thread 25T. In this case the composite thread 25T originates from a suitable beam or creel of bobbins (shown diagrammatically at 76 in
The remaining steps of the method diagrammatically illustrated in
After stitching 32 (and scouring 36, if desired) a slurry similar to that described in connection with
The resulting pile surface structure is thereafter flexed as indicated at the block 34 and optionally dried, as indicated at the block 38, both in the manner described earlier in connection with
Those skilled in the art, having the benefit of the teachings of the present invention, as hereinabove set forth, may effect numerous modifications thereto. It should be understood that all such modifications lie within the contemplation of the present invention as defined by the appended claims.
This application is a divisional of co-pending application Ser. No. 09/727,207, originally filed on Nov. 30, 2000, in the name of Dimitri Peter Zafiroglu.
Number | Date | Country | |
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Parent | 09727207 | Nov 2000 | US |
Child | 10706348 | Nov 2003 | US |